1. Field of the Invention
The present invention relates to suspension rigidity controlling apparatus and method for an automotive vehicle with a vehicular roll-over preventive feature for preventing a vehicular roll-over from occurring during a steering operation.
2. Description of the Related Art
A Japanese Patent Application First Publication No. Heisei 9-323521 published on Dec. 16, 1997 exemplifies a previously proposed vehicular roll-over preventing apparatus. In this previously proposed vehicular roll-over preventing apparatus, when detecting that a weight difference between left and right road wheels is equal to or larger than a set weight difference on the basis of a detection information from a weight detecting section and a steering state detecting section, a roll rigidity adjusting section is operated as a safety device so that a roll rigidity (stiffness) of each suspension of the vehicle is increased. Thus, a vehicular roll rigidity is suppressed. This prevents the vehicle from being rolled over.
However, since it is not possible to zero the roll of the vehicle in terms of a function that the vehicular suspension system naturally has, a dive of a vehicle body at outer (road) wheels which are one of left and right road wheels located at an outside with respect to a cornering center during a steering operation of a steering wheel of the vehicle is restricted if the roll rigidities of all vehicular suspensions are augmented at a time point at which a predetermined roll is developed due to the steering operation. Hence, when a roll angle of the vehicle is furthermore increased, a pressing force against each outer wheel which is a component force of a centrifugal force at a position of a weight center of the vehicle is decreased and a jack-up force against inner wheels (a force in a direction to lift the inner wheels in an upward direction) is varied in its increase direction. Therefore, as the roll angle of the vehicle becomes increased, a height of the weight center of the vehicle is varied in its increase direction.
As described above, when the height of the vehicular weight center under a state in which a roll moment is applied to the vehicle body is increased, the roll moment applied to the vehicle body is increased. Thus, the vehicle falls in a state in which the vehicle is easy to be rolled over. Furthermore, during a reverse steering operation to an originally steered direction, if a variation width of the roll angle becomes large due to a sway-back of a vehicle body to a sway thereon, an inertia force causes the vehicle to become easier to be rolled over.
It is, therefore, an object of the present invention to provide suspension rigidity controlling apparatus and method for an automotive vehicle which can remarkably enhance a vehicular roll-over prevention effect, with the roll moment applied to the vehicle becomes decreased by controlling a rigidity of a suspension in a direction to reduce a potential energy of a sprung mass of the vehicle when the vehicle falls in a driving state in which there is a possibility that the vehicle is rolled over.
The above-described object can be achieved by providing a vehicular suspension rigidity controlling apparatus, comprising: a plurality of suspensions, each suspension being intervened between a sprung mass of a vehicle body and an unsprung mass of a corresponding road wheel; a suspension rigidity adjusting section that is enabled to adjust a rigidity of each suspension; a driving state detecting section that detects a driving state of the vehicle; a vehicular roll-over determining section that predictively determines whether the vehicular driving state is a state in which there is a possibility that the vehicle is rolled over from the detected driving state of the vehicle; and a suspension controlling section that controllably adjusts the rigidity of at least one of the suspensions via the suspension rigidity adjusting section in a direction to decrease a potential energy of the sprung mass of the vehicle when the vehicular roll-over determining section predictively determines that the vehicular driving state is the state that there is the possibility that the vehicle is rolled over.
The above-described object can also be achieved by a vehicular suspension rigidity controlling apparatus, comprising: a plurality of suspensions, each suspension being intervened between a sprung mass of a vehicle body and an unsprung mass of a corresponding road wheel; a suspension rigidity adjusting section that is enabled to adjust a rigidity of each suspension; a driving state detecting section that detects a driving state of the vehicle including at least a vehicular velocity detecting section that detects a vehicular velocity and a steering angular velocity detecting section that detects a steering angular velocity; a vehicular roll-over determining section that compares each of the detected vehicular velocity and the steering angular velocity with a corresponding one of predetermined threshold values to predictively determine whether the driving state of the vehicle is in the state in which there is a possibility that the vehicle is rolled over; and a suspension controlling section that, when the driving state of the vehicle is transferred from a first turning state to a second turning state which is reverse to the first turning state and the vehicular roll-over determining section predictively determines that the driving state of the vehicle is in the state in which there is a possibility that the vehicle is rolled over, adjustably controls rigidities of the respective suspensions via the suspension rigidity adjusting section in such a manner that one of the rigidities at at least compression stroke of the respective suspensions have been at the compression stroke during the first turning state being decreased and the rigidities at at least extension stroke of the remaining suspensions which have been at the compression stroke during the first turning state being increased is carried out to decrease a potential energy of the sprung mass of the vehicle.
The above-described object can also be achieved by providing a vehicular suspension rigidity controlling method, the vehicle comprising: a plurality of suspensions, each suspension being intervened between a sprung mass of a vehicle body and an unsprung mass of a corresponding road wheel; and a suspension rigidity adjusting section that is enabled to adjust a rigidity of each suspension, and the method comprising: detecting a driving state of the vehicle; predictively determining whether the vehicular driving state is a state in which there is a possibility that the vehicle is rolled over from the detected driving state of the vehicle; and controllably adjusting the rigidity of at least one of the suspensions in a direction to decrease a potential energy of the sprung mass of the vehicle, when predictively determining that the vehicular driving state is the state that there is the possibility that the vehicle is rolled over.
This summary of the invention does not necessarily describe all necessary features so that the invention may also be a sub-combination of these described features.
The other objects and features of the present invention will become understood from the following description with reference to the accompany drawings.